Abrupt Climate Change
Review of last lecture
• Large spread in projected temperature change comes from uncertainties in climate feedbacks
• Main climate feedbacks for global warming: ice-albedo, temperature (lapse rate), water vapor, cloud, aerosol, carbon cycle
Observing the atmosphere: Proxy data(e.g. coral reef, tree ring, lake sediment, ice
core)
Coral reef Tree ring
Lake sediment
Ice core - The best proxy data for paleoclimate
Ohio State Ice Core Group
Ohio State Ice Core Sites
Temperature during the past 2.4 billion years - The ice ages
What is an ice age?• An ice age is a long interval of time (millions
to tens of millions of years) when global temperatures are relatively cold and large areas of the Earth are covered by continental ice sheets and alpine glaciers.
• At least five major ice ages have occurred throughout Earth’s history. Currently, we are living in an ice age!
• Records show that ice ages typically develop slowly, whereas they end more abruptly.
Extinction of mammoth
Variations within an ice age:The 100,000-year glacial cycle
Glacier distribution at the last glacial maximum about 20,000
years ago
Possible causes
• Change in atmospheric composition (e.g. CO2, CH4)
• Change in earth’s orbit (e.g. Milankovitch cycles)
• Motion of tectonic plates• Change in solar output
Abrupt climate change and tipping point– Lesson from Earth’s climate history
Video: A global warning?
Termination of the Younger Dryas cold event and last ice age 11,600
years ago
Abrupt climate change and history/politics
- Collapse of Maya civilization and Chinese ancient dynasties
Droughts
The little ice age
Pieter Bruegel the elder: Winter landscape with skaters and bird trap, 1565
Bifurcation and tipping point
Examples of tipping points
Interactions among tipping points
Summary• Ice age: a long time (millions to tens of millions of years)
of cold temperatures and extended ice cover. >5 in earth’s history (including now). Develop slowly, but end more abruptly.
• Glacial cycle: has a 100,000 year oscillation period
• Past abrupt climate change
• Tipping points